This invention relates to a multi-nozzle type ink jet recording head which jets ink in the form of a droplet from the ink cavity by utilization of a piezo-electric effect.
A method of jetting ink in the form of a droplet from the ink cavity by utilization of a piezo-electric effect has been well known in the art. FIG. 1 is a sectional view of a conventional multi-nozzle type ink jet recording head disclosed by Japanese Patent Application (OPI) No. 49033/1977 (the term "OPI" as used herein means an "unexamined published application"). In FIG. 1, reference numeral 1 designates piezo-electric element cylinders each having a liquid chamber 2. Each of the cylinders 1 is communicated through its one end to an ink supplying path 3 and through its other end to an ink passage 4. A nozzle 5 is formed at the end of each of the ink passages 4. The ink is supplied through an ink supplying inlet6 into a common supply chamber 7, where it is pooled. In the recording head, the piezo-electric element cylinders 1 are buried in an epoxy resin body 8.
In the recording head thus constructed, the piezo-electric element cylinders 1 are selectively driven to decrease the volumes of the liquid chambers 2 thereof, so that the ink in the liquid chambers 2 are jetted from the nozzles 5.
In the above-described conventional ink jet recording head, the piezo-electric element cylinders 1 are employed as means for driving the nozzles 5, and the piezo-electric element cylinders 1 are each made up of a cylinder of piezo-electric material, and an inner electrode and an outer electrode which are provided respectively on the inner wall and the outer wall of the cylinder. In order to miniaturize the ink jet recording head, it is essential to miniaturize the piezo-electric element cylinders 1 also. However, it is considerably difficult for the present manufacturing technique to manufacture a piezo-electric element cylinder extremely small both in outside diameter and in inside diameter and to form the inner electrode on the inner wall of the cylinder. For instance in the case where it is required to arrange nozzles outlets 40 .mu.m.times.40 .mu.m at intervals of 1 mm, it is impossible to miniaturize the piezo-electric element cylinders 1 to the extent that the latter 1 can be arranged at intervals of 1 mm. That is, the outside diameter of each piezo-electric element cylinder 1 should be 0.5 mm in maximum, and the inside diameter should, of course, be smaller than 0.5 mm. In addition, it is required to form the inner electrode on the inner wall of the cylinder 1. It is impossible for the current manufacturing technique to manufacture such piezo-electric element cylinders. Accordingly, the outside and inside diameters of the conventional piezo-electric element cylinders are larger than those which have been mentioned above. Therefore, the conventional ink jet recording head suffers from a difficulty that, as shown in FIG. 1, the width L.sub.2 of the body 8 is much larger than the width L.sub.1 of the nozzle 5.
In addition, it is possible but difficult to bury the small piezo-electric element cylinders 1 in the epoxy resin body 8 and to form the extremely thin ink supplying paths 3, ink passage 4 and nozzles 5 in the body 8.